Multi-pole circuit breaker interlock



March 1961 w. H. MIDDENDORF MULTI-POLE CIRCUIT BREAKER INTERLOCK 4 Sheets-Sheet 1 Filed Aug. 18, 1958 INVENTOR.

March 28, 1961 w. H. MIDDENDORF POLE CIRCUIT BREAKER INTERLOCK MULTI- 4 Sheets-Sheet 2 Filed Aug. 18, 1958 lrlllll March 28, 1961 w. H. MIDDENDORF MULTI-POLE CIRCUIT BREAKER INTERLOCK 4 Sheets-Sheet 3 Filed Aug. 18, 1958 INVENTOR.

March 28, 1961 w MIDDENDQRF 2,977,443

MULTI-POLE CIRCUIT BREAKER INTERLOCK Filed Aug. 18, 1958 4 Sheets-Sheet 4 nrroeueys.

United States Patent MULTI-POLE CIRCUIT BREAKER INTERLOCK William H. Middendorf, Covington, Ky., assignor to The Wadsworth Electric Manufacturing Company, Inn, Covington, Ky., a corporation of Kentucky Filed Aug. 18, 1958, Ser. No. 755,762

11 Claims. (Cl. 200-116) This invention relates to multi-pole circuit breakers and more particularly to an interlock design for multipole circuit breakers by which single pole circuit breakers may be adapted for multi-pole operation with simultaneous tripping of all circuit breakers when fault occurs in the circuit of any one circuit breaker.

The invention is directed to circuit breakers of the type having a movable contact bar associated with a carrier in which opening of contacts in response to current overload is effected by unlatching the carrier followed by movement of the carrier which, in turn, carries the contact bar.

In prior art designs of rriulti-pole circuit breaker operation with breakers of this general type, the multi-pole operation has been effected by engagement of one of the latch members, that is, the current-responsive member or the carrier, by some common trip device. This operation inflicts a repeated hammering on critical latch elements. Such continuous impact loading of these elements tends to alter their physical dimensions and consequently their calibration so that in time they no longer operate to open their respective circuits at their rated current overload.

The present invention eliminates the disadvantages of the prior common trip systems for circuit breakers by providing a common trip interlock which is engaged by the carrier upon tripping and has a portion which directly engages the contact bar of the adjacent circuit breaker to open the circuit of the adjacent breaker without disturbing the latch of the adjacent circuit breaker.

It has been an objective of the invention to provide a common trip interlock for multi-pole circuit breaker operation which is suitable for use with certain standard over center type breakers and which does not require a change in the disposition of the standard operating parts.

It has been a further objective of the invention to provide a common trip interlock for multi-pole circuit breaker operation in which the common trip interlock has its own spring biasing means. The interlock is designed to be disposed between adjacent breakers. By utilizing separate spring biasing means for the interlock, any number of circuit breakers may be joined together for multi-pole operation, the spring biasing interlock providing a cascade efiect to trip all circuit breakers upon overload tripping of any one circuit breaker.

Another objective of the invention has been to provide a common trip interlock system for multi-pole circuit breaker operation as described in the preceding paragraph in which latch means are provided to hold the interlock in a non-tripping position against the biasing of the spring. The latch means may include an actual latch abutment engaged by the interlock, or, alternatively, a latched condition may be provided by connecting the interlock biasing spring for over center operation with respect to the interlock pivot axis.

It has been another objective of the invention to provide such a spring biased interlock in which the spring biasing of the interlock does not afiect the sensitivity of the circuit breaker.

A still further objective of the invention has been to provide a springless common trip interlock for multipole circuit breaker operation in which the interlock is engaged by the carrier and driven thereby upon tripping, the operating parts having a leverage design by which the interlock will apply a force to the contact bar in a direction to open the contact bar, the force being approximately two times the force of the spring holding the contact bar in closed condition.

It has been another objective of the invention to provide a multi-pole circuit breaker system in which each breaker is provided with means for indicating that tripping has occurred, the indicia means being operated only by the circuit breaker which has been tripped due to overload. This objective is attained by relating the position of the indicia means with the condition of the carrier. Thus, the carrier which snaps to open condition due to overload will operate the indicia means whereas the adjoining circuit breakers will be opened without disturbing the latched carriers and consequently without disturbing their respective indicia means.

These and other objectives of the invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a side elevational view of a circuit breaker and interlock constructed in accordance with the present invention;

Fig. 2 is an end elevational view, partly in section, thereof;

Fig. 3 is a perspective View of the interlock per se;

Figs. 4-7 are fragmentary views in elevation showing the stages of operation of the interlock;

Fig. 8 is an alternative embodiment of an interlock;

Figs. 9-12 are fragmentary views in elevation showing the stages of operation of the interlock;

Fig. 13 is still another alternative embodiment of the interlock;

Figs. l417 are fragmentary views partly in elevation showing the stages of operation of the interlock; and

Fig. 18 is a fragmentary view of the indicia operator.

The circuit breaker of the type to which the present invention is applicable is illustrated in Figs. 1 and 2 with the standard operating parts being shown principally in broken lines. These standard parts form no part of the present invention except insofar as they cooperate with the interlock to provide the common trip operation.

The principal elements for a standard type of circuit breaker include the casing 20, the slidable operating handle 21 projecting above the casing and acting on a handle lever 22 pivoted at its lower end 23 to the casing 20. A spring 24 is connected at one end 25 to the handle lever 22 and at the other end 26 to a movable contact bar 27. The upper end 28 of the contact arm is received in an inverted V-shaped slot 30 provided in a rocket or carrier 31. The carrier 31 is pivoted at one end 32 to the casing for movement between a latched position as shown in Fig. l and an unlatched position as shown in Fig. 6.

The carrier latch includes a latching projection 33 which cooperates with a latch surface 34 at the upper end of a current responsive bimetallic element 35. The lower end of the current responsive element is integrally secured as at 36 to a strap 37 which forms a part of one of the circuit breaker terminal connectors. The contact bar 27 carries a movable contact 38 which cooperates with a fixed contact 40 secured to a strap 41. The strap 41 terminates in a pair of jaws 42 designed to grip a bus bar blade (not shown) to form the other terminal connector. The circuit through the breaker follows a path 3 from the strap 37 through the bimetal 35, a pigtail 43, the contact bar 27, the contacts 38 and 40, and the strap 41 to the jaws 42.

The closed condition of the breaker is illustrated in Fig. 4. The movable contact 38 is held against the fixed contact lit by tension spring 24., the contact arm 27 hearing against and being pivotally urged counterclockwise about the point of engagement of its upper end 28 with the carrier 31. The spring 24 also acts on the carrier 31 through the contact arm 27 to urge the carrier in a clockwise direction about its. pivot point 32. Pivoting of the carrier is prevented by engagement of the carrier latch projection 33 with the current-responsive latch surface 34. 1

Upon release of the latch, the breaker elements move to the position shown in Fig. 6. The carrier 31 pivots about its pivot point 32, carrying with it the contact bar 27 and thereby opening the contacts 38 and 40.

Manual opening of the contacts is not illustrated but consists simply in sliding the operating handle 21 to its leftmost position which pivots the sliding lever 22 angularly toward the left as viewed in Fig. 4. The movement toward the left of the operating lever 22- causes the spring 24 to move over center with respect to the pivoting end 28-of the contact arm thereby causing the contact arm to pivot and bringing the contacts out of engagement with each other.

As indicated above, the elements of the circuit breaker and their operation thus far described are known and do not of themselves form a part of the invention.

Common trip interlock In multi-pole operation, two or more circuit breakers are rigidly connected in side-by-side relationship with operating handles 21 ganged together by handle ties 48 as shown in Fig. 2. The most common forms of multipole operation utilize two interconnected breakers for one or two phase circuits, or three interconnected breakers for three phase circuits. The common trip aspect of the contacts of such interconnected breakers is controlled by an interlock mechanism.

The common trip interlock 49 is illustrated in Fig. 3 and includes a plate 50 having an elongated pivotal slot 51. At the upper end of the plate are provided a projection 52 cooperating with the operating lever '22 for resetting the interlock and a bar 53 engageable by carriers of all circuit breakers connected together for multi-pole operation The bar 55 may be a unitary member extending through all adjoining circuit breakers thereby tying together the operation of the respective interlock plates, as shown in Fig. 2.

At the lower end of the plate 50 is a projection 54 which is engageable with the contact arms 27 of the adjoining circuit breakers. The projections 54 on respective plates Stl are separate from each other as illustrated in Fig. 2 to permit individual type action, or, as conversely expressed, to avoid making the position of the projection 54 of one plate 50 be precisely dependent upon the position of the projection 54 of another plate.

The interlock 49 is mounted to each carrier, as illustrated in Fig. l. The carrier casing has a pivot stud 55 which receives the elongated slot 51 to permit both pivotal and sliding movement of the interlock with respect to the carrier casing. Elongated slots 56, 57, and 58 are formed in the casing wall to receive projection 52, bar 53, and projection 54 respectively.

An interlock tension spring 60 is connected at one end 61 to a hole 62 formed in the plate 50 and at the other end 63 to a stud 64 on the casing wall. The tension spring biases the interlock for clockwise rotation and for bodily upward movement as viewed in Fig. l. A plate latch 65 is fixed to the wall of the breaker and is. engageable by a portion on of the upper edge of the plate 50 to resist upward and rotational movement of the interlock when the interlock is in the latched condition illustrated in Fig. 4.

Interlock operation When the carrier is in a contacts-closed condition, the main carrier elements and the interlock are disposed as illustrated in Fig. 4. When overload occurs, the carrier and bimetal latch elements will become disengaged, whereby the spring 24 rotates the carrier 31 and contact bar 27 to the position shown in Fig. 6. As carrier 31 begins to rotate, it engages the bar 53. In the first portion of the movement of the carrier, the carrier causes a slight pivoting and downward sliding movement of the plate Sllsufficient to cause edge portion 66 of the plate to disengage itself from the plate latch 65 (as shown in Fig. 5). Immediately following the disengagement of the edge 66 from the plate latch 65, the tension spring 60 takes over and snaps the plate St) to the position shown in Fig. 6.

Figs. 4 and 6 illustrate the change in condition of the elements of the breaker. in which the fault occurred. Fig. 1 illustrates the change in the disposition of corresponding elements of the adjoining breakers. It can be seen from Fig. 1 that the carrier remains in its latched condition. The plate mounted projection 54, however, has, during the spring biased clockwise rotation of the plate, engaged the contact bar 27 to snap it to open position. Thus, on the faulted breaker the carrier has shifted its position to initiate the operation of the interlock; whereas in the adjoining breakers, where no fault has occurred, the rotation of the platehas left the carriers undisturbed but through the force of the spring 66, the interlock has snapped the conatct bar 27 to the open position.

Resetting of the interlockautomatically occurs when the circuit breaker operating handle is moved for normal circuit breaker resetting. In resetting a circuit breaker of this type, the operating handle is first moved toward the left to swing the carrier back into latched engagement with the current-responsive element 35. The handle is then rotatedto the right to the position shown in Fig. l to snap the contact bar 27 and its contact into. engagement with he fixedcontact 40. In moving be operating handle 21 to the left, the operating lever 22 is pivoted counterclockwise as illustrated in Fig. 7. in its counterclockwise movement it engages the projection 52, causing the interlock plate 50 to pivot counterclockwisely. The upper left corner 67 of the plate 54) engages an inclined surface 68 on the latch 65, the inclined surface camming the plate 50 downwardly so that the plate can continue the clockwise pivoting until latching of edge 66 with the plate latch is effected.

Interlock with over center spring latch In the embodiment shown in Figs. 8-12, the operation of the interlock is similar to that of the embodiment first described and for ease of description like numerals will be applied to parts having like orientation and function. The plate 50 has the projection 52 for engagement by the operating lever 22, the bar 53 for engagement by the carrier 31, and the projection 54 which engages the contact bar 27. In this embodiment the plate is formed with a hole 70 which receives the pivot stud for purely pivotal movement. A spring 71 is connected at one end 72 to the stud 64- and at the other end 73 to an over center link 74. The link 74 is recessed at 75 to cooperate with the stud 55. The other end 76 of the link is connected to the plate 5%] by a hole 77 therein. The recess 75 brings the line of force of the spring between stud 64 and hole 77 above the pivot axis provided by stud 55 when the interlock is in the condition shown in Fig. 9, thereby urging the plate 50 to pivot counterclockwise. It can be seen that as the plate 50 is caused to pivot slightly in the clockwise direction, the line of force of the spring 71 will be brought below the pivot axis and the spring will thereafter cause the plate to pivot in a clockwise direction.

Operation of interlock with over center spring latch When a fault occurs on the circuit breaker, the carrier is unlatched as before and engages the plate projection 53.

The force of the spring loaded carrier 31 is sufiicient to overcome the bias of spring 71 on the plate when the elements are positioned as shown in Fig. 9 and will cause the plae to rotate to the position shown in Fig. 10. From the position of Fig. 10, the spring 71 takes over and snaps the plate 50 to the position of Fig. 11. The rotation of the plate to the position of Fig. 11 causes the projection 54, extending through to the adjoining circuit breaker to engage the contact bar 27 of the adjoining breaker and to snap the contact bar to open position. The movement of the contact bar of the adjoining circuit breaker to open position is effected without disturbing the latched condition of its carrier 31 so that the operating parts of the adjoining breakers, except for the contact bar, remain in the position of Fig. 11.

It will be appreciated that Fig. 10 is illustrative of the condition of the parts of the breaker upon which fault has occurred, whereas Fig. 11 is illustrative of the main operating parts of the adjoining circuit breakers.

Resetting of the interlock is accomplished in a manner similar to that of the previous embodiment, that is, the resetting will take place automatically upon reclosing of the circuit breaker system. In reclosing the contacts of the circuit breakers, the operating lever 22 is pivoted toward the left by moving the operating handle (as shown in Fig. 1) toward the left. The pivotal movement of the operating lever causes the engagement of the lever with the projection 52 as shown in Fig. 12 to rotate the plate 50 in a counterclockwise direction, thereby returning it to the positionof Fig. 9.

Interlock utilizing carrier sprinlg force interlock. The interlock of this embodiment relies on the spring force of the carrier to open the contacts of the adjoining breakers. The interlock of this embodiment is, due to the limitations of the spring force obtainable from anyone carrier spring, not particularly suitable for the cascade operation of large number of circuit break ers. However, due to its simplicity of construction, it is ideally suited for double or triple pole operation.

In the embodiment of Figs. 1317, an interlock plate 80 is provided with projections 81 at the upper end thereof engageable by the carrier 31 and projections 82 at the lower end thereof which are engageable with the contact bar 27. The plate 80 has a hole 83 which receives the stud 55 on the circuit breaker wall for pure pivotal movement.

Operation of interlock utilizing carrier spring force In the on condition of the breaker, the operating parts appear as illustrated in Fig. 14. Upon tripping of the breaker due to fault, the operating parts shift to the position of Fig. 15. In tripping, the carrier 31 rotates clockwise, bearing against the projection 81 and rotatively'driving the plate 80. The corresponding operation for the adjoining circuit breakers is illustrated in Fig. 16. By comparing Fig. 16 with Fig. 14, it is seen that while the carrier of the adjoining breaker remains undisturbed in its latching condition, the rotation of the plate 80 has caused the lower projection 82 to snap the contact bar 27 to the open position.

It should be noted that the principal breaker operating spring 24 is involved in the performance of the operation of all of the moving elements. In other words, spring 24 on the adjoining circuit breakers tends to hold the contact bar 27 in the contact closed position. An identical spring 24, however, on the faulted breaker, through the pivoting of the carrier 31, causes the contact bar 27 to be driven, through the plate 80, to the open position. It can be demonstrated through a diagramming of the lever arms and points of application of the spring force, that the spring force from the faulted breaker tending to open the contacts on the adjoining breakers is at least twice the spring force on the adjoining breakers tending to maintain the contacts closed. The ratio of forces may, of course, be varied within limits by design of the elements and their points of interconnection. Thus, two and three pole operation is possible utilizing the springless interlock of Figs. 13-17.

Resetting of the circuit breakers automatically accomplishes resetting of the interlock following tripping. To understand the resetting, it should be appreciated that the contact arms on the adjoining breakers are maintained, by the springs 24, in their condition of counterclockwise bias toward closed position as indicated by the arrow in Fig. 16. They are prevented from pivoting to closed position by their engagement with interlock projection 82 which is, in turn, maintained in the position of Fig. 16 by the greater force of the spring on the carrier 31 bearing against the plate 80. When a faulted breaker is reset as described in connection with the first embodiment, the carrier 31 is shifted back to its latched position as shown in Fig. 17, thereby freeing the plate from the force of the spring on the faulted breaker. Release of the plate 80 enables the spring biased contact arms 27 to drive the plate 80 back to the position of Fig. 14.

Trip indicator A very desirable feature of the common trip interlock which operates only on the contact bars leaving their carriers undisturbed is illustrated in Fig. 18.

Circuit breakers of the type described are provided with a small red indicator button 85 connected to a corner 86 on the carrier by a small spring 37. When the carrier becomes unlatched, the corner 86 of the carrier acts through spring 87 to drive button 85 upwardly to the broken line position indicating that the carrier has been tripped.

Meanwhile, the adjoining breakers have had their contacts driven to open position by the interlock, but their carriers remain undisturbed. As a consequence, the indicator buttons of the adjoining carriers also remain undisturbed. Thus, one wishing to remedy the fault which has caused the operation of the breakers can immediately identify the line on which the fault has occurred by observing the projected position of the indicator button which is found only on the faulted carrier.

In a general manner, while there has been disclosed in the above description, what is deemed to be the most practical and eflicient embodiment of the invention, it should be well understood that the invention is not limited to such embodiment as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

Having described my invention, I claim:

1. A common trip interlock for at least two circuit breakers joined in side by side relation, each circuit breaker having a movable carrier and a current responsive latch associated therewith, a movable contact bar engageable with a fixed contact and carried by said carrier but movable with respect thereto, and spring means biasing said carrier and movable contact selectively toward closed and tripped positions, said interlock comprising: a plate movably mounted on said breakers, first projections on said plate engageable by any one of said carriers when said carrier is moved upon unlatching, and second projections on said plate engaging the contact bar on the adjoining breaker to move said contact bar out of engagement with said fixed contact.

2. A common trip interlock for at least two circuit breakers joined in side by side relation, each circuit breaker having a movable carrier and a current responsive latch. associated therewith, interconnected handle means on each breaker for manually moving said lever,

a movable contact bar engageable with a fixed contact and carried by said carrier but movable with respect thereto, and spring means biasing said carrier and movable contact selectively toward closed and tripped positions, said interlock comprising: a plate movably mounted on said breakers, first projections on said plate engageable by any one of said carriers when said carrier is moved upon unlatching, second projections on said plate engaging the contact bar on the adjoining breaker to move said contact bar out of engagement with said fixed contact, and a third projection on said plate engageable by said lever to reset said plate after tripping.

3. A common trip interlock for at least two circuit breakers joined in side by side relation, each circuit breaker having a movable carrier and a current responsive latch associated therewith, a movable contact bar engageable with a fixed contact and carried by said carrier but movable with respect thereto, and spring means biasing said carrier and movable contact selectively toward closed and tripped positions, said interlock comprising: aplate mounted on said breakers, said plate being movable between rese and tripped positions, spring means biasing said plate toward tripped position, latch means normally maintaining said plate in reset position, first projections on said plate engageable by any one of said carriers when said carrier is moved to unlatch said plate for movement to tripped position, and second projections on said plate engaging the contact bar on the adjoining breaker when said plate is moved to tripped position to move said contact bar out of engagement with said fixed contact.

4. An interlock according to claim 3 in which said latch means comprises a fixed latch on one of said breakers engageable by said plate in reset position, means mounting said plate for pivotal and sliding movement whereby said plate may be slid away from said fixed latch and thereafterpivoted to tripped position.

5. An interlock according to claim 3 in which said latch means comprises: means pivotally mounting said plate, and means connecting said spring means between said plate and one of said circuit breakers for over center operation with respect to said plate pivot axis, whereby said spring means will normally maintain said plate in reset position until said carrier pivots said plate past the over center position and thereafter said spring means will snap said plate to reset position.

6. A common trip interlock for at least two circuit breakers joined in side by side relation, each circuit breaker having a movable carrier and a current responsive-latch associated therewith, a movable contact bar engageable with a fixed contact and carried by said carrier but movable with respect thereto, and spring means bias.- ing said carrier and movable contact selectively toward closed and tripped positions, said interlock compris ing: a plate mounted on said breakers for movement between reset and tripped positions, first projections on said plate engageable by any one of said carriers when said carrier is moved upon unlatching to move said plate to tripped position, and second projections on said plate engaging the contact bar on the adjoining breaker tomove said contact bar out of engagement with said fixed contact when said plate moves to tripped position.

7. A common trip interlock for at least two circuit breakers joined in side by side relation, each circuit breaker having a carrier movable between tripped and reset positions and a current responsive latch associated with said carrier, indicia means operable by said carrier to show the tripped and reset condition of said carrier, a movable contact bar engageable with a fixed contact and carried by said carrier but movable with respect thereto, and spring means biasing said carrier and movable contact selectively toward closed and tripped positions, said interlock comprising: a plate movably mounted on said breakers, first projections on said plate engageable by any one of said carriers when said carrier is moved to tripped position and second projections. on"

said plate engaging the contact bars on'the adjoining breakers to move said contact bar on the breaker adpacent to the tripped breaker out of engagement with said fixed contact, whereby the contacts on both breakers will be opened and the indicia means on only the breaker in the line in which the fault occurred will show a tripped condition.

8. A cascade interlock for a plurality of circuit breakers joined in side by side relation: comprising a plurality of interconnected interlock means disposed between adjacent circuit breakers and movable between reset and tripped positions, spring means connected to each said interlock means and urging each said interlock means toward tripped position, latch means normally maintaining each said interlock means in reset condition and operable upon tripping of any of said breakers to eifect unlatching ofall said interlock means, and means on each said interlock means for opening the contacts of the adjacent breakers when said interlock means is moved to tripped position, whereby the tripping of any circuit breaker will effect the opening of all circuit breakers through the action of said spring biased interlock means.

9. An interlock according to claim 8 further comprising indicia means on each said circuit breaker for indicating which of said circuit breakers has been tripped through fault,

10. A common trip interlock for at least two circuit breakers joined in side by siderelation, each circuit breaker having a movable carrier and a current responsive latch associated therewith, a movable contact bar engageable with a fixed contact and carried by said carrier but movable with respect thereto, and spring means biasing said carrier and movable contact selectively toward closed and tripped positions, said interlock comprising: a plate disposed between adjacent breakers, a latch fixed on one of said breakers and engageable by said plate, a pivot post and slot mounting said plate on oneof said breakers for pivoting movement between tripped position and reset position in which said plate engages said latch and sliding movement into and out of engagement with said latch, a spring'connected between said plate andone of said breakers urging said plate slidably toward said latch and pivotally away from said latch toward tripped position.

11. A common trip interlock for at least two circuit breakers joined in side by side relation, each circuit breaker having a movable carrier and a current responsive latch associated therewith, a movable contact bar engageable with a fixed contact and carried by said carrier but movable with respect thereto, and spring means biasing said carrier and movable contact selectively toward close and tripped positions, said interlock comprising: a plate, means pivotally mounting said plate between adjacent breakers, a tension spring connected between said plate and one of said breakers for overcenter opera tion with respect to said pivot means, said spring normally maintaining said plate in a reset" position, said spring, when moved past said pivot means pivoting said plate to a tripped position, first projections on said plate engageable by any one of said carriers when said carrier is moved upon unlatching to pivot said plate from reset position thereby bringing said spring past said pivot means, and second projections on said plate engaging the contact bar onthe adjoining breaker when said plate is pivoted to tripped position to move said contact bar out of engagement with said fixed contact.

References Cited in the file of this patent UNITED STATES PATENTS (Other references on foiiowing page) 9 UNITED STATES PATENTS Walle Dec. 22, 1942 Leonard May 4, 1943 Brumfield May 11, 1954 Thomas Jan. 29, 1957 Dorfman et a1 June 25, 1957 10 Mascioli et a1 Nov. 12, 1957 Hagdahl Dec. 17, 1957 Christensen Feb. 18, 1958 Platz Sept. 22, 1959 FOREIGN PATENTS Great Britain Aug. 1944 

